I have UIPageViewController that animates programatically. The problem is that the view controllers inside it has UIButtons inside them. When I hold down a button and wait until the UIPageViewController animates, the app crashes with the error:
'Failed to determine navigation direction for scroll'
What I think I need to do is to somehow fake that the user releases the button before the UIPageviewController animates.
However, [self.button sendActionsForControlEvents:UIControlEventTouchCancel]; doesn't seem to do the trick. Neither do UIControlEventTouchUpInside.
Is there a better way do to it or am I using sendActionsForControlEvents wrong?
All sendActionsForControlEvents: does is call any methods you've assigned to the control events passed in for the button. It doesn't call any internal methods to programmatically lift up touches or anything like that.
Right before you programmatically animate your page view controller, try using this method to effectively cancel any touches on the pan gesture recognizer of the page view controller's internal scroll view:
- (void)cancelPanGestureTouchesOfPageViewController:(UIPageViewController *)pageVC
{
// Since UIPageViewController doesn't provide any API to access its scroll view,
// we have to find it ourselves by manually looping through its view's subviews.
for (UIScrollView *scrollView in pageVC.view.subviews) {
if ([scrollView isKindOfClass:[UIScrollView class]]) {
// We've found the scroll view, so use this little trick to
// effectively cancel any touches on its pan gesture recognizer
BOOL enabled = scrollView.panGestureRecognizer.enabled;
scrollView.panGestureRecognizer.enabled = !enabled;
scrollView.panGestureRecognizer.enabled = enabled;
}
}
}
(Note that this is messing with the internal view hierarchy of UIPageViewController, so this method is kind of ugly and may break in the future. I generally don't recommend doing stuff like this, but I think in this instance it should be okay.)
Related
I have added a subview to a View Controller's view. This subview is the view of QLPreviewController.
What I am trying to achieve is to recognize swipe gestures on the subview in the parent view, i.e. the View Controller's view. In the end, I want to be able to swipe left /right on the view to load the next document for preview.
I'm aware of hit testing and understand that by just attaching a gesture recognizer to the parent view, those will not be recognized, since the subview will be the "hit-test" view.
Now what is the best (or easiest) way to recognize those gestures?
Note: I didn't manage to attach the gesture recognizers to the subview, this doesn't seem to work.
* UPDATE *
To make this more clear - this is the code from my ViewController. vContent is just a view in my ViewController, where I add the view of the QLPreviewController:
let pvVc = QLPreviewController()
pvVc.dataSource = self
vContent.addSubview(pvVc.view)
I tried adding the swipe recognizers both to the vContent and the pvVc.view. In both cases no event was fired.
let sgrLeft: UISwipeGestureRecognizer = UISwipeGestureRecognizer(target: self, action:Selector("handleSwipe:"))
sgrLeft.direction = UISwipeGestureRecognizerDirection.Left
sgrLeft.delegate = self
On some other view the code works fine.
Any hint is appreciated!
Thx
Eau
Well, the responder chain, the unknown animal … ;-)
You can subclass the superview and override -hitTest:forEvent:.
You rarely need to call this method yourself, but you might override it to hide touch events from subviews.
Gesture Recognizers Get the First Opportunity to Recognize a Touch, so even the subview is hitTest view. the gestureRecognizer attached on superView can recognizer touch event.
I have a navigation controller that pushes a view-controller (PARENT) that contains an UIPageViewController (PAGES). Now I used pan/swipe gestures to switch between the children of the page-view-controller. However, I can no longer pop the PARENT-view controller using the swipe gesture from the left border of the screen, because it is interpreted as a gesture in PAGES.
Is it possible to accomplish that swipe-to-pop when the left-most view-controller is shown?
Two ideas:
Return nil in pageViewController:viewControllerBeforeViewController -> doesn't work.
Restrict the touch area, as described here.
Or is there a more straightforward way?
I had the same situation as #smallwisdom, but handled it differently.
I have a view controller A that I push on top of my navigation controller's stack.
This view controller A contains a horizontal scroll view that stretches all the way from left side of the screen to the right.
In this scenario, when I wanted to swipe the screen to pop view controller A from navigation controller's stack, all I ended up doing was scrolling this horizontal scroll view.
The solution is pretty simple.
Inside my view controller A, I have code like this:
_contentScrollView = [[UIScrollView alloc] init];
[self.view addSubview:_contentScrollView];
for (UIGestureRecognizer *gestureRecognizer in _contentScrollView.gestureRecognizers) {
[gestureRecognizer requireGestureRecognizerToFail:self.navigationController.interactivePopGestureRecognizer];
}
It works great. What this does?
It is telling the scrollView's gesture recognizers that they have to wait to see if some other gesture recognizer will recognize the current gesture.
If that other fails to recognize, then they will no longer have to wait and they can try to recognize the current gesture.
If that other recognizer succeeds and recognizes the current gesture, then all of the gesture recognizers that have been waiting will automatically fail.
This other gesture recognizer they have to wait is set to be the navigation controller's interactivePopGestureRecognizer. He is in charge for the swipe-to-go-back gestures.
I mostly agree with #ancajic's answer. I would like to provide an extra-case when you set UIPageViewController's transitionStyle to 'Scroll', in which you'll not get gestureRecognizers to be set, the workaround is:
if (self.navigationController?.interactivePopGestureRecognizer != nil)
{
for view in self.pageViewController!.view.subviews
{
if let scrollView = view as? UIScrollView
{
scrollView.panGestureRecognizer.requireGestureRecognizerToFail(self.navigationController!.interactivePopGestureRecognizer!);
}
}
}
I had a similar issue in one of my projects and used the following method. In my case, it was one of those left-side menus that were really popular before iOS 7.
My solution was to set the UINavigationControllerDelegate and then implemented the following:
- (void)navigationController:(UINavigationController *)navigationController
didShowViewController:(UIViewController *)viewController
animated:(BOOL)animated {
// enable the interactive menu gesture only if at root, otherwise enable the pop gesture
BOOL isRoot = (navigationController.viewControllers.firstObject == viewController);
self.panGestureRecognizer.enabled = isRoot;
navigationController.interactivePopGestureRecognizer.enabled = !self.panGestureRecognizer.enabled;
}
EDIT:
Additionally, you need a hook into the UIPageViewController's gesture recognizers. (They aren't returned by the gestureRecognizers property for a scroll view style page view controller.) It's annoying, but the only way I've found to access this is to iterate through the scrollview's gesture recognizers and look for the pan gesture. Then set a pointer to it and enable/disable based on whether or not you are currently displaying the left-most view controller.
If you want to keep the right swipe enabled, then replace the pan gesture with a subclassed pan gesture recognizer of your own that can conditionally recognize based on the direction of the pan gesture.
First, find UIPageViewController's scrollView
extension UIPageViewController {
var bk_scrollView: UIScrollView? {
if let v = view as? UIScrollView {
return v
}
// view.subviews 只有一个元素，其类型是 _UIQueuingScrollView，是 UIScrollView 的子类
// view.subviews have only one item of which the type is _UIQueuingScrollView, which is kind of UIScrollView's subclass.
for v in view.subviews where v is UIScrollView {
return v as? UIScrollView
}
return nil
}
}
Second, set gestureRecognizer's dependence.
override func viewDidLoad() {
super.viewDidLoad()
if let ges = navigationController?.interactivePopGestureRecognizer {
pageViewController.bk_scrollView?.panGestureRecognizer.require(toFail: ges)
}
}
Swift version of #Lcsky's answer:
if let interactivePopGesture = self.navigationController?.interactivePopGestureRecognizer, let pageViewController = self.swipeVC?.pageViewController {
let subView = pageViewController.view.subviews
for view in subView {
if let scrollView = view as? UIScrollView{
scrollView.panGestureRecognizer.require(toFail: interactivePopGesture)
}
}
}
UITapGestureRecognizer is applied to both UIImageView and its subview (UITextView). However, when I tap on subview, the receiver becomes subview and its parent view (i.e. UIImageView + UITextView). It should however be only subview because that was the one I tapped. I was assuming nested gestures would react first but apparently parent receives the fist tap and then it goes to child.
So, there are different solutions out there for various scenarios (not similar to mine but rather buttons inside scroll view conflict). How can I easily fix my issue without possible subclassing and for iOS 6+ support? I tried delaying touch on start for UIGestureRecognizer on UIImageView and I tried setting cancelsTouchesInView to NO - all with no luck.
Try the following code:
conform the <UIGestureRecognizerDelegate> to your class.
set yourGesture.delegate = self;
then add this delegate Method:
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
// return YES (the default) to allow the gesture recognizer to examine the touch object, NO to prevent the gesture recognizer from seeing this touch object.
if([touch.view isKindOfClass: [UITextView class]] == YES)] {
return YES;
}
else {
return NO;
}
}
Hope it will solve your issue. Enjoy Coding..!!!!
That's exactly what is it supposed to do.
View hierarchy is like a tree structure and its traversal during a touch gesture starts from the root node. It is very likely for your parent view to receive gesture first and then its subviews. The traversal skips the nodes for which
userInteractionEnabled = NO.
since, you don't have any code I can't help you to play with this flag. A more general solution is to always set gesture only for your parentView and in the gesture delegates check the coordinates if it belongs to any one of the subview and if yes then call your gesture method for your subview.
Not a clean approach but works. !!
you should implement the UIGestureRecognizer delegate methods and apply the correct policy to the gesture, when multiple gesture are recognized
I have a Custom Scroll View, subclassing UIScrollView. I have added a scroll view in my viewcontroller nib file and changed its class to CustomScrollView. Now, this custom scroll view (made from xib) is added as a subview on self.view.
In this scroll view, I have 3 text fields and 1 UIImageView(named signImageView) added from xib. On clicking UIImageView (added a TapGestureRecogniser), a UIView named signView is added on the custom scroll view. I want to allow User to sign on this view, So I have created a class Signature.m and .h, subclassing UIView and implemented the touches methods (touchesBegan, touchesMoved and touchesEnded) and initialised the signView as follows:
signView = [[Signature alloc]initWithFrame:signImageView.frame];
[customScrollView addSubview:signView];
But when I start signing on the signView, the view gets scrolled and hence the touches methods don't get called.
I have tried adding signView on self.view instead of custom scroll view, but in that case the view remains glued to a fixed position when I start scrolling. (Its frame remains fixed in this case)
Try setting canCancelContentTouches of the scrollView to NO and delaysContentTouches to YES.
EDIT:
I see that similiar question was answered here Drag & sweep with Cocoa on iPhone (the answer is exactly the same).
If the user tap-n-holds the signView (for about 0.3-0.5 seconds) then view's touchesBegan: method gets fired and all events from that moment on go to the signView until touchesEnded: is called.
If user quickly swipes trough the signView then UIScrollView takes over.
Since you already have UIView subclassed with touchesBegan: method implemented maybe you could somehow indicate to user that your app is prepared for him to sign ('green light' equivalent).
You could also use touchesEnded: to turn off this green light.
It might be better if you add signImageView as as subView of signView (instead of to customScrollView) and hide it when touchesBegan: is fired). You would add signView to customScrollview at the same place where you add signImageView in existing code instead.
With this you achieve that there is effectively only one subView on that place (for better touch-passing efficiency. And you could achieve that green light effect by un-hiding signImageView in touchesBegan:/touchesEnded:
If this app-behaviour (0.3-0.5s delay) is unacceptable then you'd also need to subclass UIScrollView. There Vignesh's method of overriding UIScrollView's touchesShouldBegin: could come to the rescue. There you could possibly detect if the touch accoured in signView and pass it to that view immediately.
When ever you add a scrollview in your view hierarchy it swallows all touches.Hence you are not getting the touches began. So to get the touches in your signon view you will have to pass the touches to signon view. This is how you do it.
We achieved this with a UIScrollView subclass that disables the pan gesture recogniser for a list of views that you provide.
class PanGestureSelectiveScrollView: UIScrollView {
var disablePanOnViews: [UIView]?
override func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
guard let disablePanOnViews = disablePanOnViews else {
return super.gestureRecognizerShouldBegin(gestureRecognizer)
}
let touchPoint = gestureRecognizer.location(in: self)
let isTouchingAnyDisablingView = disablePanOnViews.first { $0.frame.contains(touchPoint) } != nil
if gestureRecognizer === panGestureRecognizer && isTouchingAnyDisablingView {
return false
}
return true
}
}
Views in my iPad app behave as if they prevent their superview's gesture recognizers from firing when the user initiates such gesture in that view.
Is this expected?
How can I remove that shielding behavior?
What are good practices to debug gesture recognizers?
In more details:
The main "canvas" view of my application, lets the user adds shapes to it with a "long double tap". I attached a gesture recognizer for such gestures to the main view. That works very well: the main view gets called, and reacts by adding a shape to the main view.
Shapes are implemented as subviews of the main view. When the user long-double-taps in the main view, my code instanciate a shape subview, and adds it to the main view. Shape views can be moved around with a long-single-tap recognizer. So I also attach a gesture recognizer for long-single-taps to every shape view. That works very well: the shape view gets called and lets the user move it in the canvas.
However, when the user long-double-taps in a shape view, nothing happens: the shape view is not called, which is expected since it doesn't have a gesture recognizer for long-double-taps. But the main view is not called either. I had thought that since the gesture was not recognized by the shape view, then it would be propagated up in the responder chain to the main view. But this doesn't happen.
My intent is to let the user add overlapping shapes to the main view, so that a long-double-tap on a shape would also add a new shape to the main view.
What could I have missed?
I can of course add a long-double-tap recognizer to shape views, and from there, either forward the gesture to the main view or handle the gesture directly in a way similar to what I do in the main view.
But this sounds wasteful, and more importantly, I'd like to understand the behavior.
Thanks for any suggestion.
It should as far as I can see pass the message along out of the box.
To ensure both gestureRecognizers are not fired you need to do something like:
[longPress requireGestureRecognizerToFail:doubleLongPress];
Update
Just free styling here but if you want to limit the gesture to one view you could try playing with the gesture delegate (this will only respond if the touched view is self.view)
self.myGesture.delegate = self;
In your controller do something like:
//.h
#interface MyController : UIViewController <UIGestureRecognizerDelegate>
// ...
#end
//.m
#implementation MyController
//...
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch;
{
BOOL shouldReceiveTouch = YES;
if (gestureRecognizer == self.myGesture) {
shouldReceiveTouch = (touch.view == self.view);
}
return shouldReceiveTouch;
}
//...
#end
NB I haven't tested this but I will update when I test it later.